We are currently performing whole exome sequencing (WES) with appropriate follow up to identify important genetic factors associated with Cushing's disease (CD) and related abnormal physical features. The ultimate goal is to identify a genetic variant or variants that cause CD. CD is a condition in which the pituitary gland produces inappropriately high levels of adrenocorticotropic hormone (ACTH). The ACTH stimulates the adrenal gland to produce excess cortisol, leading to clinical disease. CD is caused by ACTH secreting pituitary tumors. It is noteworthy that patients who have CD also have abnormal features: abnormal facial features including abnormal facial height and nasal length. CD is a serious condition. It requires surgery to remove the tumor. The tumors sometimes recur in which case radiation or medical therapy is required which is not always successful. CD can cause a wide range of problems due to the high cortisol levels. These include diabetes, fractures, poor growth, and hypertension. CD can be fatal. Whole exome sequencing (WES) is a powerful tool for identifying important genetic variants associated with medical conditions. It is an efficient method of determining the genetic code (sequence) of all the regions in the genome that are translated into protein, the exons. The exons constitute about 1% of DNA, thus sequencing exons provides a large amount of information at a fraction of the cost of sequencing the entire genome. Another advantage of the exome sequencing approach is that the areas of the genome sequenced are those for which data interpretation is the most robust. WES is now one of the most important methods for genetic investigation because it provides data on the coding regions of the genome and because it is a cost effective method of searching for important genetic variants. Pediatric aged patients seen at NICHD with a confirmed diagnosis of CD are evaluated for this study. Those who have histopathologically confirmed disease in conjunction with DNA, hormonal documentation of the disease and complete clinical data are potential cases. Cases have been selected and whole exome sequencing performed. Analysis comparing variants found in the cases with large control populations has been done. In addition, the data are being examined for copy number variants in the exons to determine if they play a role in Cushing's disease. A second stage is progressing. Whole exome sequencing has now been performed on tumor tissue in patients where tumor tissue is available to determine if there are specific tumor-associated variants in the exome. In addition, samples from patients who have ectopic posterior pituitaries have been obtained and whole exome sequenced. The first publications from this project have now been published. We have shown that somatic USP8 mutations, a cause of Cushing disease in adults, is also a common cause in children. We have also identified a novel cause of Cushing disease, loss of function mutations in the CABLES1 gene. Investigations of other variants are ongoing.